Female electrical terminals are provided in electrical connectors for mating with male electrical terminals, such as sockets for receiving terminal pins. A widely used type of terminal is stamped and formed of sheet metal material in a generally U-shaped cross-section, often used in a multi-contact electrical connector.
With female terminals of the character described above, such as a socket for receiving a terminal pin, a contact force is exerted by the socket on the pin, transversely of the direction of insertion of the pin, to form a stable electrical connection between the socket and the pin. Such female terminals or sockets most often have cantilevered spring contact arms exerting the transverse force on the pin. In order to achieve a very strong or stable electrical connection between the inserted pin and the socket, the spring contact arms exert a relatively high force on the pin. Therefore, the force required to insert the pin into the socket also is relatively high. The greater the spring force, the greater the insertion force of the pin into the socket.
On the other hand, high insertion forces can be undesirable in multi-contact electrical connectors where the number of mating terminals is quite high. Consequently, there constantly is an effort to design the terminals with an acceptable insertion force along with an acceptable contact force. One such design attempt is shown in U.S. Pat. No. 4,687,278 to Grabbe et al, dated Aug. 18, 1987 (which also refers to U.S. Pat. No. 4,550,972). These patents show spring contact beams or arms which have apexes or dimples which engage the inserted male terminal or pin to establish the contact forces on the pin as well as determining the insertion force of the pin into its socket. These patents offset or axially space the apexes or dimples so that they are engaged by the pin sequentially during movement of the pin into the socket. Such offsetting of the apexes or dimples reduces the insertion force on the inserted pin because the pin will not effectively deflect the spring contact beams or arms simultaneously.
A problem with providing spring contact beams or arms with offset or axially spaced pin-engaging apexes or dimples is that the beam length or moment arms of the spring contact arms end up being different and, consequently, different spring contact arms exert different contact forces on the pin. This invention is directed to solving that problem and compensating for the offset or staggered dimple configuration by correspondingly varying the effective beam lengths of the spring contact arms.